where \(\mathcal {A} = A / 2\pi \sigma _{12} \ell _c^2\)  is a dimensionless Hamaker constant.
Using the values of \(Ca\) , \(\sigma _{12}\)  and \(\ell _c\)  reported in § REF , as well as the typical dimensional Hamaker constant \(|A| \approx 10^{-20}~\)  for water-oil-air systems [1]}, we estimate \(\mathcal {A} \approx 1.6 \times 10^{-14}\) .
